my Apache has "MaxKeepAliveRequests 100" and "KeepAliveTimeout 5". As i look up my site via browser i can refresh as often as I want. But after waiting 5 seconds with doing nothing and then refreshing, the server won't answer anymore but is still active as a process.

With "KeepAlive Off" the server hang-up with the second request.The connection is established via WAN-IP to the server which is behind a router.Even looking at a folder leads to that error.